1. Field of the Invention
The present invention relates in general to tool chucks for attachment of accessories to power drivers.
2. Description of Related Art
A variety of tool chucks have been developed in which the chuck jaws may be opened and closed via a relative rotation between parts of the tool chuck. In some applications, the tool chuck may include a sleeve that is rotatable manually (with or without using a chuck key) to open and close the chuck jaws. In other applications, power from the power driver may be utilized to open and close the chuck jaws. For example, the tool chuck may be provided with a sleeve that is axially moveable to a position in which the sleeve is grounded (i.e., rotationally fixed) to the housing of the power driver. Thus, when the driver is powered up, a spindle of the driver (and consequently a chuck body) may rotate relative to the sleeve. The relative rotation between the spindle and the sleeve may open and close the chuck jaws.
Conventional keyless tool chucks are not without shortcomings. For example, the tightening or loosening torque applied during a chuck actuation process may vary depending on factors such as, for example, the firmness with which the operator manipulates the sleeve. On the one hand, if an operator manipulates the sleeve with a relatively high force, then a relatively high torque may be applied during the chuck actuation process. On the other hand, if an operator manipulates the sleeve with a relatively low force, then a relatively low torque may be applied during the chuck actuation process.
The inconsistent application of torque may lead to problems such as under-tightening and over-tightening of the tool chuck. When the tool chuck is under tightened, the accessory may slip relative to (and even inadvertently fall from) the tool chuck. When the tool chuck is over-tightened, it may be difficult to loosen the tool chuck to remove the accessory. Also, high speed impacts between transmission elements of the power driver may occur when the chuck jaws bottom out on the accessory (when tightening) or when the chuck jaws reach the full limit of travel (when loosening). In conventional power tool or other power devices, such high speed impacts may damage the transmission elements, since the torque applied during the chuck actuation process may be unlimited.